Just tried it out of curiosity.
It is indeed working quite well.
Made a new menu as described here
Activated wiki parsing for this menu.
Made a Major menu Option, in your case PRODUCTS with no link.
Then an intended menu option without link where i didnt put in Text as usual but the Plugininclude as described above (replace foo with a Tiki site where the required links for the Mega Menu are in).
This is really working. Lets find useful applications for it.
I followed all the steps above, but I am not getting the output I want. I think maybe the problem is with the links in the include plugin. Can you send me a screenshot of how the menu you created looks?